HUMANS SEEING HUMANS

Abstract

Three studies examined the impact of social stimuli on visual attention. Chapter two confirmed that, hands, feet, and bodies exhibited equivalent attentional pull in a dot probe detection, two-alternative forced choice paradigm. Chapter three utilized a Posner style covert attentional cueing paradigm to examine the impact of directed human action (throwing a ball) on spatial attention. We manipulated the effect of context by including social (humans) or non-social (trees) flanking images and probed the uniquely social nature of the processing in this task by including individuals with autism spectrum disorder (ASD), a group with known social deficits, as a comparison group. We also manipulated predictability using predictive and non-predictive cue blocks between subjects. Participants with and without ASD demonstrated similar cueing effects when cues were predictive. ASD participants showed no cueing advantage when cues were non-predictive while neurotypical participants experienced cueing only in social contexts when cues were non-predictive – consistent with automatic social processing. Intelligence as measured by the FSIQ from the WAIS 4 was also analyzed. Unexpectedly, higher IQ resulted in slower RTs with the ASD group. We examined this relationship further by examining severity of diagnosis measured by ADOS-G and FSIQ in participants with ASD. In a final study we looked at the relationship between RT and eye movements in visual search for social stimuli like faces and bodies. Consistent with previous results, faces resulted in faster RTs when they were the targets. They also elicited more first fixations and shorter fixation durations. Faces were not, however, more distracting when they appeared in irrelevant singleton frames. Unexpectedly, the bodies images used in this experiment did not result in attentional capture. Possible reasons for this are discussed.